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Isocitrate dehydrogenase [NAD] subunit alpha, mitochondrial



Canis lupus familiaris (Dog) (Canis familiaris)
Reviewed-Annotation score: Annotation score: 3 out of 5-Experimental evidence at protein leveli


Catalytic subunit of the enzyme which catalyzes the decarboxylation of isocitrate (ICT) into alpha-ketoglutarate. The heterodimer composed of the alpha (IDH3A) and beta (IDH3B) subunits and the heterodimer composed of the alpha (IDH3A) and gamma (IDH3G) subunits, have considerable basal activity but the full activity of the heterotetramer (containing two subunits of IDH3A, one of IDH3B and one of IDH3G) requires the assembly and cooperative function of both heterodimers.By similarity

Catalytic activityi

Isocitrate + NAD+ = 2-oxoglutarate + CO2 + NADH.

Enzyme regulationi

The heterotetramer and the heterodimer composed of IDH3A and IDH3G subunits can be allosterically activated by citrate (CIT) or/and ADP, and the two activators can act independently or synergistically. The heterodimer composed of IDH3A and IDH3B subunits cannot be allosterically regulated and the allosteric regulation of the heterotetramer is through the IDH3G subunit and not the IDH3B subunit. The IDH3G subunit contains the allosteric site which consists of a CIT-binding site and an ADP-binding site, and the binding of CIT and ADP causes conformational changes at the allosteric site which are transmitted to the active site in the catalytic subunit (IDH3A) through a cascade of conformational changes at the heterodimer interface, leading to stabilization of the isocitrate-binding at the active site and thus activation of the enzyme. ATP can activate the heterotetramer and the heterodimer composed of IDH3A and IDH3G subunits at low concentrations but inhibits their activities at high concentrations, whereas ATP exhibits only inhibitory effect on the heterodimer composed of IDH3A and IDH3B subunits.By similarity

GO - Molecular functioni

GO - Biological processi


Molecular functionOxidoreductase
Biological processTricarboxylic acid cycle

Names & Taxonomyi

Protein namesi
Recommended name:
Isocitrate dehydrogenase [NAD] subunit alpha, mitochondrial (EC:
Alternative name(s):
Isocitric dehydrogenase subunit alpha
NAD(+)-specific ICDH subunit alpha
Gene namesi
OrganismiCanis lupus familiaris (Dog) (Canis familiaris)
Taxonomic identifieri9615 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaLaurasiatheriaCarnivoraCaniformiaCanidaeCanis
  • UP000002254 Componenti: Unplaced

Subcellular locationi

Extracellular region or secreted Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertionGraphics by Christian Stolte; Source: COMPARTMENTS

Keywords - Cellular componenti


PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
ChainiPRO_00000835891 – ›13Isocitrate dehydrogenase [NAD] subunit alpha, mitochondrialAdd BLAST›13

2D gel databases



Subunit structurei

Heterooligomer of subunits alpha (IDH3A), beta (IDH3B), and gamma (IDH3G) in the apparent ratio of 2:1:1. The heterodimer containing one IDH3A and one IDH3B subunit and the heterodimer containing one IDH3A and one IDH3G subunit assemble into a heterotetramer (which contains two subunits of IDH3A, one of IDH3B and one of IDH3G) and further into the heterooctamer.By similarity

Family & Domainsi

Sequence similaritiesi


Sequence statusi: Fragment.

Mass (Da):1,356
Last modified:October 1, 1996 - v1

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Non-terminal residuei131

Entry informationi

Entry nameiIDH3A_CANLF
AccessioniPrimary (citable) accession number: P54836
Entry historyiIntegrated into UniProtKB/Swiss-Prot: October 1, 1996
Last sequence update: October 1, 1996
Last modified: September 27, 2017
This is version 56 of the entry and version 1 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program


Keywords - Technical termi

Complete proteome, Direct protein sequencing, Reference proteome


  1. SIMILARITY comments
    Index of protein domains and families